Production of material libraries using sputter methods

ABSTRACT

In a process for the combinatorial production of a library of materials in the form of a two-dimensional matrix in the surface region of a planar substrate by sputtering, the planar target used for the sputtering is arranged in parallel to the planar substrate and has surface regions of different chemical composition.

[0001] The invention relates to processes for the combinatorialproduction of a library of materials in the surface region of a planarsubstrate by sputtering.

[0002] The parallelized production and testing of materials havingsuitable physical and/or chemical properties is a sector in materialresearch which is currently greatly increasing in importance.

[0003] WO 98/47613 discloses a number of processes by which, usingsputtering, CVD or PVD techniques, libraries of materials of potentialinterest can be generated. Basically, this application relates to theuse of suitable masking techniques which makes possible defineddeposition of at least two components (which are present as separatesubstrates) on one substrate, as a result of which composite materialsare obtained. In addition, by means of the process, by generatinggradients on the sputtered substrate, complete libraries of materials ofdiffering composition can be generated.

[0004] The use of numerous different masks, which need to be positionedexactly to obtain reliable results, makes the process described complexto carry out.

[0005] It is an object of the present invention to provide a process forthe combinatorial production of a library of materials, which processavoids the disadvantages of the known process.

[0006] We have found that this object is achieved by a process for thecombinatorial production of a library of materials in the form of atwo-dimensional matrix in the surface region of a planar substrate bysputtering, with the planar target used for the sputtering beingarranged in parallel to the planar substrate and having surface regionsof different chemical composition (e.g. a mosaic target).

[0007] In addition, the object is achieved according to the invention bya process for the combinatorial production of a library of materials inthe surface region of a planar substrate by sputtering, with aribbon-shaped substrate being shifted in the longitudinal direction andat least two targets of different chemical compositions which are usedfor the sputtering being arranged over the ribbon along the direction ofshifting.

[0008] In the present invention the use of masks for generating thedesired libraries is avoided, so that producing libraries isconsiderably simplified.

[0009] The fundamental idea of the mosaic target is that a materiallyinhomogeneous target for sputtering is used for the sputtering process,with a matrix of unknown composition being first produced by thesputtering process. Not until after successful testing for the desiredphysical or chemical property is the composition analyzed of thematerials complying with the requirements. By coating the basic targetwith various other components, a gradient of the different components isproduced on the sputtered matrix during the sputtering process. Thisgradient can be useful for producing alloys of metals and/or nonmetals,mixed oxides of metals and/or nonmetals or other classes of compounds ofdifferent compositions, provided that they are accessible by means ofsputtering processes. By a suitable spatial arrangement of thecomponents on the basic target, the sputtered matrix can be divided intosectors in which, in the manner of set theory, enrichment in each caseof one of the components occurs, so that as great a range as possible ofthe potentially producible component mixtures can be generated.

[0010] Sputtering is the atomization of a solid surface by bombardmentwith high-energy ions such as O⁺ or Ar⁺ or neutral particles (FAB, fastatom beam bombardment). In sputtering, the kinetic energy of the primaryparticle, that is of the ions or neutral particles, is distributed byimpact to the atoms of the solid (target). If in this process sufficientenergy is transferred to a surface atom to overcome the surface bindingenergy, this can leave the solid as a free particle and be deposited ona substrate. In this manner, individual atoms, ions and clusters can begenerated and deposited on substrates. The kinetic energy of the ions orneutral particles is generally from 0.1 to 20 keV. Suitable sputteringprocesses are known. Since the particles released have higher energiesthan thermally vaporized particles, they can be used for depositing thinlayers on substrates, compared with what are termed PVD processes(Physical Vapor Deposition processes).

[0011] By selecting a target having surface regions of differentcomposition, composition gradients of the material resulting on asubstrate can be produced. Gradients of this type can also be achievedaccording to the invention by the material substrate being shiftedspatially along a number of targets, the targets being excited in aphase-shifted manner.

[0012] Hitherto, sputtering processes have been used to generatecompositions which are as homogeneous as possible, and not forgenerating gradients, cf. Ullmanns Encyclopedia of Industrial Chemistry,6th Edition, 1998 Electronic Release, Wiley-VCH, Weinheim, Germany.

[0013] The term “library of materials” means that a multiplicity ofmaterials of different composition are generated on a substrate.Preferably, at least 10, particularly preferably at least 100, differentmaterials are formed on the substrate.

[0014] The expression “in the surface region” means that the materialsare formed, for example, on a planar substrate, with the sputteredmetals or nonmetals not penetrating into the substrate. This is thecase, in particular, in the case of smooth ceramic, glass, plastic,metal, or carbon substrates. However, corresponding porous supportmaterials can also be used, with the sputtered metals or nonmetalspenetrating at least into the surface pores. In this case, according tothe invention the material is formed in the topmost layer of the planarsubstrate, that is to say in the surface region.

[0015] The expression “planar substrate” means a substrate which extendsconsiderably further in two directions in space than in the thirddirection in space. The planar substrate need not be flat, it can, forexample, be a series of depressions or wells on or in a plate. Forexample, it can be a spot plate or a corresponding plate which hasdepressions at regular intervals. In particular, the porous supportmaterial can also be present in the form of bodies of any shape, forexample in the form of tubes which have been cut open and divided intotwo halves that can be rejoined for a subsequent catalytic test.Preference is given to porous support materials made of ceramics, metalsor activated carbons. Examples of such supports are described inDE-A-198 05 719 as auxiliary supports.

[0016] The exact configuration of the planar substrate is notrestricted. Preferably, the planar substrate is subdivided intoindividual defined places which are spatially delimited from oneanother.

[0017] The expression “planar target” denotes a target which extendsconsiderably further in two directions in space than in the thirddirection in space. The planar target, like the planar substrate, neednot necessarily be flat. It can be provided on the surface, at least inpart, with planar metal pieces and/or nonmetal pieces of at least onemetal or nonmetal different from the target. The pieces can be fixed,for example, by glueing, soldering or welding. The spatial extension canthen be chosen during the sputtering. The planar target can be arranged,for example, horizontally and can be coated on the surface at least inpart with planar metal pieces and/or nonmetal pieces of at least onemetal or nonmetal which is different from the target. In this case thetarget is sputtered from above.

[0018] The planar target is arranged in parallel to the planarsubstrate. This ensures that on the planar substrate a matrix ofdifferent materials is formed during the sputtering, since regions ofdifferent material compositions are present on the target. Slightdeviations from parallelity of, for example, ±5°, preferably ±2°, can betolerated in this case.

[0019] The target has surface regions of differing composition. In thiscase, at at least two different spatial positions of the target,different surface compositions are present.

[0020] For example, a target can be coated at different positions withfoil pieces of different metal foils and/or nonmetal foils, as a resultof which, in a simple manner, a planar target is obtained having surfaceregions of different chemical composition.

[0021] Preferably, the target is coated with metal pieces and/ornonmetal pieces which are selected from metals of groups Ib, IIb, IIIb,IVb, Vb, VIb, VIIb and VIII, lanthanides and actinides, and also metalsand nonmetals of groups Ia, IIa, IIIa, IVa, Va and VIa of the PeriodicTable of the Elements. The sputtering process can be carried out for alarge range of metals and nonmetals.

[0022] Preferably, from two to twenty, particularly preferably from twoto ten, in particular from two to five, different metal pieces and/ornonmetal pieces are present on the target.

[0023] For example, the target used can be a noble metal target such asa gold target that is coated in a suitable manner with other noble metalfoil pieces such as platinum foil pieces and palladium foil pieces. Forexample, also, an iron target can be coated in a suitable manner withfoil pieces of the elements gold, platinum and nickel. The foil piecescan be arranged on the target by chance or according to defined orderingprinciples. Preferably, foil pieces of different composition arearranged in such a manner that as many different material compositionsas possible result in different regions on the planar substrate (mosaictarget). On the planar substrate, not only are the compositionsaccording to the individual foil pieces obtained, but also mixtures oftwo or more thereof.

[0024] The sputtered matrix can also be subdivided into ordered sectors,for example into a two-dimensional matrix, which is coated with the foilpieces according to combinatorial principles.

[0025] The sputtering parameters are selected according to the inventionin such a manner as to give an (overlapping) distribution of thediffering components on the substrate and thus the respectivecomposition of the differing samples.

[0026] The resulting layer thickness of sputtered material can vary froma monoatomic layer to about 500 μm.

[0027] The invention also relates to a process for the combinatorialproduction of a library of materials in the surface region of a planarsubstrate by sputtering, with a ribbon-shaped substrate being shifted inthe longitudinal direction and at least two targets of differingchemical composition used for the sputtering being arranged over theribbon along the direction of shifting.

[0028] In this case it is a continuous process, preferably for coatingribbons by moving the ribbon in one direction with simultaneous coatingby different targets by means of sputtering. Instead of a target coatedwith, for example, foils, a plurality of targets of differingcomposition are arranged over the transportable ribbon in the directionof the ribbon. The two or more targets are then excited, preferably, ina phase-shifted manner in such a manner that different materials aredeposited on the ribbon-shaped substrate in the direction of the ribbon.This can be achieved, for example, by the current intensity of theindividual targets being varied in a phase-shifted manner for theindividual components as a function of time with the ribbon running at aconstant speed. The resulting ribbon then has different compositionsover its entire length and can be tested for useful properties in theindividual sections. Suitable ribbon materials are metal ribbons, metalnets, woven metal cloths, knitted metal cloths or felted metal clothswhich can be cut into pieces for the testing for useful catalyticproperties and then analyzed. They can be processed, for example, toform tubes. The type of the ribbon material is not restricted to metals,but the carrier can, as described above, also be made up of glass,ceramics or activated carbon. Ceramics which can be used are, inparticular, oxides, nitrides and carbides as glass ceramics or sinteredquartz. Reference may be made in turn to DE-A-198 05 719.

[0029] For example, three different targets arranged one behind theother can be excited according to a respectively shifted sawtoothfunction, so that in each case only two targets act on one position ofthe substrate and binary mixtures with gradients are obtained.

[0030] The invention also relates to a process for the combinatorialtesting of libraries of materials which are obtained by one of theabovementioned processes in which individual defined places of thesubstrate are analyzed for a desired property by physical and/orchemical methods and the composition of the defined places of thesubstrate for which the desired property was found is then analyzed. Theanalysis can also be carried out as described in DE-A-198 05 719.

[0031] The invention will be described in more detail below withreference to an example:

[0032] A round disk-shaped GeSb₂Te₄ target having a diameter of 15 cmwas coated using Co chips having a diameter of 1 cm at a distance of 5cm. On the matrix obtained by sputtering, cobalt contents of from 1.8 to3.6% were measured. It is implied therefrom that due to inhomogeneousarrangement of such metal chip coatings on a target, inhomogeneouscoatings on a matrix are also obtained, since the inhomogeneous coatingof the target is carried over to the sputtered surface.

We claim:
 1. A process for the combinatorial production of a library ofmaterials in the form of a two-dimensional matrix in the surface regionof a planar substrate by sputtering, which comprises the planar targetused for the sputtering being arranged in parallel to the planarsubstrate and having surface regions of different chemical composition.2. A process as claimed in claim 1, wherein the planar target isprovided on the surface at least in part with planar metal pieces and/ornonmetal pieces of at least one metal or nonmetal which is differentfrom the target.
 3. A process as claimed in claim 1 or 2, whereinsputtering is carried out using high-energy ions or neutral particles.4. A process as claimed in claim 2 or 3, wherein the target is coatedwith metal pieces and/or nonmetal pieces which are selected from metalsof groups Ib, IIb, IIIb, IVb, Vb, VIb, VIIb and VIII, lanthanides andactinides, and metals and nonmetals of groups Ia, IIa, IIIa, IVa, Va andVIa of the Periodic Table of the Elements.
 5. A process as claimed inone of claims 1 to 4, wherein the planar substrate is subdivided intoindividual defined places which are spatially delimited from oneanother.
 6. A process as claimed in one of claims 1 to 5, wherein theplanar substrate has at least on the surface a porous support materialwhich can be present in the form of shaped bodies.
 7. A process for thecombinatorial production of a library of materials in the surface regionof a planar substrate by sputtering, which comprises a ribbon-shapedsubstrate being shifted in the longitudinal direction and at least twotargets of different chemical compositions which are used for thesputtering being arranged over the ribbon along the direction ofshifting.
 8. A process as claimed in claim 7, wherein the two or moretargets are excited in a phase-shifted manner in such a manner thatdifferent materials are deposited on the ribbon-shaped substrate in thedirection of the ribbon.
 9. A process as claimed in one of claims 1 to8, wherein the planar substrate is made up at least on the surface ofglass, ceramics, metal and/or activated carbon.
 10. A process for thecombinatorial testing of libraries of materials which are obtained by aprocess as claimed in one of claims 1 to 9, in which individual definedplaces of the substrate are analyzed for a desired property by physicaland/or chemical methods and then the composition of the defined placesof the substrate for which the desired property was found is analyzed.